The Feb. 2 spill of coal ash into North Carolina’s Dan River has cost Duke Energy $15 million so far, the company reported Thursday.

The figure, reported in a securities filing, reflects costs through March 31.

Duke said total costs of the spill, which dumped up to 39,000 tons of ash into the river near Eden, are not expected to be “material” to the company.

“Material” refers to costs that are expected to have a significant impact on Duke’s earnings. Duke earned $2.7 billion in 2013.

CEO Lynn Good has said Duke will bear the costs of cleaning up the Dan, where a 70-mile trail of ash reaches Kerr Reservoir on the North Carolina-Virginia line.

But Duke has said it will ask the N.C. Utilities Commission to pass costs to customers for closing its 33 ash basins across the state.

Duke said in Thursday’s filing that the Dan response and other expenses, including the costs of new laws and regulations, lawsuits, environmental damage and operating changes, “cannot be reasonably estimated at this time.”

A federal grand jury has subpoenaed Duke and N.C. Department of Environment and Natural Resources employees as part of a criminal probe. The Environmental Protection Agency has joined state officials in investigating the spill. DENR’s four lawsuits against Duke over ash contamination are before a judge.

Legislators, meanwhile, will convene next month and are mulling new ash measures. Gov. Pat McCrory unveiled proposed legislation this week that would tighten some standards but would not make Duke remove all its ash ponds.